The number of Internet of Things (IoT) devices connected wirelessly may reach twenty billion by the year 2020, leading to the intense coexistence of wireless technologies. For spectrum efficiency under dense deployment, many of today's wireless technologies are designed to share the unlicensed/open spectrum (e.g., industrial, scientific, and medical (ISM) radio bands), including such popular technologies as WiFi®, Bluetooth®, Long-Term Evolution (LTE), and ZigBee®. Despite the common belief that coexistence of wireless technologies leads to harmful interference, it in fact offers new opportunities for those technologies to collaborate.
The traditional way of communicating among heterogeneous devices is to deploy multi-radio gateways, which suffers from several drawbacks including additional hardware cost, complicated network structure, and increased traffic overhead due to traffic flowing into and out from the gateway. To address these issues, latest literature introduces Cross-technology communication (CTC) techniques that achieve direct communication among heterogeneous wireless devices with incompatible physical (PHY) layers, using legacy devices. Such techniques commonly use packet-level modulations, where the combinations of timing and durations of packets convey the data.